1. Field of the Invention
The present invention relates to a method for selectively inhibiting reuptake of serotonin and norepinephrine using yeast extract, in other words, a yeast extract or yeast-derived bioactive peptide having an activity of selectively inhibiting reuptake of serotonin and norepinephrine, which can be effectively used in preventing or treating various diseases related to reuptake of serotonin and norepinephrine, especially depression, anxiety, stress, fatigue and obesity. The yeast extract or yeast-derived bioactive peptide also has activities as an anti-stress agent, an anti-fatigue agent, premenstrual syndrome and menstrual pain relaxant, and a brain-neurotrophic factor.
2. Description of Related Art
Depression is one of the major psychiatric disorders. About 10% of world population has suffered from depression, of which the prevalence rate is increasing recently (Bland, 1997). Depression having symptoms to suppress emotion and reduce interest and pleasure can reduce efficiency of work and ability of logical communication of the patients and make the patients to commit suicide in serious case (Johnson et al., 1992).
There are several reasons for depression. As a biological reason, abnormality of neurotransmitter can induce a depression. Actually, action of brain such as our thought and emotion is understood to be generated by change of the neurotransmitter. Among them, depression is known to be generated by deficiency or hypofunction of serotonin and norepinephrine which are neurotransmitters connecting between nerves. Therefore, in order to treat the depression, a drug which can normalize or accumulate the said neurotransmitters should be administered.
In the brain, chemical signals are transferred by neurotransmitters derived from neurons. The neurotransmitters are secreted at a synapse in which signal transfer between neurons takes place. As shown in FIG. 1, the signal transfer can properly function when synthesis (1), secretion (2), receptor binding (3), reuptake (4) and degradation (5) of the neurotransmitter are balanced. If the reuptake is unduly excessive, the neurotransmitter becomes deficient.
As a conventional anti-depression drug used clinically, there are tri-cyclic antidepressants (TCAs), selective serotonin reuptake inhibitors (SSRIs), monoamine oxidase inhibitors (MAOIs) and indeterminate antidepressants (Atypicals). The TCAs can inhibit the transfer of amine transmitters (serotonin, norepinephrine, dopamine) to neural end. The SSRIs is a drug having a priority in treating depression (Masand Gupta, 1999), however, it was reported that administration of SSRI (fluoxetine) to an old person can induce apoplexy or orthostatic hypertension (Cherin et al., 1997). The TCAs and MAOIs can reinforce the activity of serotonin and norepinephrine and inhibit cholinic, histaminic, α-1-adrenalinic receptor regions. However, they can induce various side effects by reacting with many other drugs (Pacher et al., 2001).
Anxiety induces a confusion of emotion, thought, action and physical activity (Sonavane et al., 2002). The anxiety was reported to be generated by abnormal neuro-transfer of serotonin and dopamine (Nakamura et al., 2001). Benzodiazepine drug is a synthetic compound most frequently prescribed to treat anxiety or depression (Longo and Johnson, 2000). However, long-term administration of the benzodiaxepine drug can induce lowering of cognition (Rickels et al., 1983) and physical dependence and tolerance (Ashton, 1984).
Obesity is caused from breakage of balance of appetite control and metabolic control in the body. An important target for treating the obesity is to induce suppression of appetite by increase the level of brain serotonin which is one of the appetite suppressing neurotransmitter. If the secretion of serotonin is increased in the brain, the appetite is suppressed. This was found in the process of treating depression patient, where many depression patients administered with antidepressant increasing serotonin amount experience had experience of decreasing of appetite. Fenfluramine, dexfenfluramine and sibutramine which are prescribed to obesity patients have an activity to selectively inhibit reuptake of serotonin and norepinephrine in pre-synaptic neuron and therefore increase the level of serotonin in the synapse (Richard J et al., J Nutr Biochem 9, 511-515, 1998; Ljung, T et al., J of internal medicine 250(30), 219-224, 2001).
Modern peoples suffer from various types of daily stress. Emotional changes caused by such stress affect the autonomic nervous system, hormone secretion, and immune system in the human body and further ones' overall heath.
In general, when the human body is stressed, due to stimulation of the sympathetic part of the autonomic nervous system, secretion of hormones, in particular, adrenaline, is triggered (Corrodi H, Fuxe K, Hokfelt T.; The effect of immobilization stress on the activity of central monoaminergic neuron, Life Science 7: 108-112, 1968). To inhibit continuous stimulation of the sympathetic part, the parasympathetic part is spontaneously stimulated to secrete acetylcholine, and thus the body maintains balance in the autonomic nervous system. However, when the human body is subjected to excess stress for a long period of time, the body is too exhausted to effectively manage the stress accumulated in the sympathetic part, so balance in the autonomic nervous system is destroyed and directly affect the mechanisms of cellular and humoral immunity, thereby causing immunodeficiency, functional disorders. This abnormal state if it is prolonged causes organ disorders.
As a result, peptic ulcer, hypertension, cancer, diabetes, irritable colon syndrome, cardiopathy, bronchial asthma, tension headache, arthritis, neurodermatitis, etc. may result. Typical symptoms include liability to fatigue, impatience in daily life, inability to fall into a deep sleep, chills, sweating, shoulder pains, oppressed feeling, feeling as if something is in throat, dizziness, hyposexuality for males, and infertility for females.
To alleviate those stress disorder, conventionally, psychotropics have been used; for example, minor tranquillizers such as diazepam, meprobamate, methylpentinol, and etifoxine; neuroleptics such as chloropromazin, promethazine, and azapaerone; beta-adrenergic antagonist such as bunitrol; antidepressants such as a triple- or quadruple-ring compound, which are used alone or together with a neuropleptic; psycoanaleptics such as caffeine, amphetamine, or derivatives thereof; and sedatives and hypnotics such as a phenobarbital-codeine complex (Poldinger, W., Schmidlin, P. E., Wider, F., Index Psychopharmacorum, H. Buber, Bern). However, the use of those psychotropics relies on pharmacotherapy for relief of a predominant symptom without pathological consideration of the cause of the stress and cannot reduce chromatic damages caused from the stress. Also, the psychotropics cannot resist the stress through catabolic regeneration but rather inhibits a normal reaction in that body is adapted to stress and causes a number of adverse effects. Typically, Human body develops tolerance to the antianxiety agents and psychoanaleptics such as amphetamine or caffeine and thus dosage of above drugs need to be increased. A significant adverse effect is that there is the probability of becoming dependent on the psychoactive agent.
To eliminate such imbalance in the autonomic nervous system due to stress, many attempts have been made in a variety of aspects. In particular, stress is medically defined as a negative stimulus destructing the body's homeostasis. Neurotransmitters are involved in the negative stimulus. Acetylcholine derived from cholesterol, described above, is an important neurotransmitter. Acetylcholine, a relaxation-inducing neurotransmitter, is secreted from the parasympathetic part of the autonomic nervous system. About 50 other neurotransmitters have been discovered so far.
Such a neurotransmitter needs a complementary counterpart called a “receptor” for it to function. Although a number of neurotransmitters exist, the neurotransmitters cannot function properly if there is no receptor having a peptide structure to be coupled to the neurotransmitter. A muscarinic receptor, which is coupled to acetylcholine, is composed of peptides including aspartic and glutamic residues, which are important for the coupling, and hydrophobic amino acids surrounding the residues (Gearien 1999). When a neurotrophic factor including these peptides is supplied to the body, nerve cells are nourished and grown to treat a variety of neuropathies, such as Parkinson's disease, without side effects. By accelerating the generation of sufficient neurotransmitters and their receptors, impulses on nervous system by excess stress (stimuli) can be absorbed and delivered without causing a load to the nerve cells, thereby treating stress disorders. In other words, to intensify the nervous system, it is important to take in peptides acting as a neurotrophic factor to generate neurotransmitter receptors as well as neurotransmitters themselves. Since receptor peptides react depending on the amount of neurotransmitters, there is no side effect due to the excess dose of the receptor peptide.
A “brain-neurotrophic factor” refers to a neurotrophin for nerve tissues, such as the brain and spinal marrow, to accelerate the growth of the nerve cells or neuroglia cells. In the past, it was believed that brain nerve cells could not be grown. However, since then it has been discovered that brain nerve cells grow and proliferate with the supply of a particular neurotrophic factor and interest in studying neurotrophins has been increased. Accordingly, neurotrophins to regulate the growth and proliferation of nerve cells and their peptide sequences have been discovered with fetal and animal brains. Neurotrophins having peptides capable of accelerating the growth and proliferation of the nerve cells or neuroglia cells have been known to be effective for the treatment of functional disorders caused from nerve cell degeneration, such as Parkinson's disease and Alzheimer's disease (Varon and Bunge 1997, Ann. Rev. Neuroscicence 1:327; Thoenen and Edgar 1985, Science 229:238).
Significant neurotrophic factors found to date, include nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), glial cell-derived neurotrophic factor (GDNF), Neurotrophin-3 (NT-3), NT-4/5, etc., which are kinds of peptides. However, use of a human or fetal brain to find a new neurotrophic factor raises ethical issues, because it is extracted from a corpus, and the amount of neurotrophic factor is too trace to be detected in the brain. So, only a few neurotrophic factors have been found up to now. Therefore, many kinds of neurotrophic factors, more than those identified to date, are predicted to exist.
Conventionally, a neurotrophic factor or neurotransmitter has been obtained by preparing a synthetic peptide or recombinant peptide using a peptide synthesizer or a genetic recombinant technique through polymerization chain reaction (PCR), respectively. However, these techniques are costly and cause a safety problem, thereby limiting commercial applications. Most synthetic or recombinant peptides are macromolecules of 30,000 daltons or greater, so they cannot pass through a brain blood barrier and reach a brain nerve cell through a brain blood barrier by oral administration, and thus direct injection into the brain is necessary (Medical Report 1998, Editions of Jan. and Feb.).
Therefore, it would be desirable to prepare a neurotropic peptide, using a yeast extract or yeast peptide derived from a food-grade yeast as in the present invention, having anti-stress, anti-fatigue, anti-anxiety, and deep sleep-inducing effects with a comparatively small dose, without using complicated processes of the genetic recombination method. This neurotropic peptide derived from the yeast according to the present invention can be widely applied for commercial use, compared to conventional neurotropic factors (Neurotrphin, NT-3, BDNF, NGF, etc.) identified by genetic recombination and does not cause a safety problem, such as suspicion of a genetic mutant.
Yeast, generally recognized as safe (GRAS) for the human body, contains 50% or more quality proteins, excess minerals, vitamin B, etc., so it has been widely used in the liquor or bakery industry as a source of protein, nucleic acids, enzymes, liquids, vitamins, minerals, etc. (Roman et al., Food Biotechnology, 6, 225, 1992). Yeast extracts produced by autolytic enzyme or other proteases have been used as a source of microorganism fermentation media, seasonings, and health foods (Bioindustry, 14, 53, 1997). However, the functionality of the yeast extract hydrolyzed from yeast or yeast-derived peptides and their specific use as an anti-stress agent and a native brain-neurotrophic factor through experimental assays have not been reported yet. Also, the production of anti-stress and anti-anxiety agents, sleeping drugs, and other medicines using the yeast-derived peptides has not been disclosed. In addition, the effect of the yeast extract on premenstrual syndromes similar to stress symptoms or on menstrual pains is not known.
Premenstrual syndromes (PMS) refer to symptoms experienced by fertile women during their menstrual cycle after ovulation, including physical symptoms such as cramp pain, low back pain, peycalgia, abdominal bloating, diarrhea, constipation, and breast fullness and tenderness, and emotional symptoms such as anxiety, irritability, depression, insomnia, fatigue, reduction in concentration, idioctonia impulse, etc. Those symptoms are similar to stress symptoms and are experienced by 70% of all women, unendurable to 20% of those women, thereby causing social and economical losses due to the inability to work.
Menstrual pains refer to mild or incapacitating cramp pains or low back pain generally experienced by most women, about 50% of all fertile women, combined with PMS before, after, or during their menstrual cycle. Mostly, young women within 1 or 2 years after their menarche suffer from menstrual pains, but this may be sustained into their forties. Reportedly, about 10% of those feels so painful not to able to ordinary work for 1 to 3 days a month. According to the result of a survey by Kyunghee University Oriental Medicine Hospital, 47% suffered from menstrual cramp pain, low back pain, and more seriously, headaches, during their menstrual cycle, 13% experienced disturbance gastrointestinal such as anorexia and indigestion, and 8% had disesthesia. In particular, about 70% of 632 middle and high school girls, 50% of those seriously, experienced menstrual pains. Such serious symptoms for the students are believed to be due to stress from excess schoolwork and examination. It was also investigated that above 90% of those basically do not manage their pain, 66% of those endure the pain without any treatment, and 28% of those take analgesics.
In spite of the efforts made by many researchers over a long period of time, the causes of PMS or menstrual pains have not been accurately identified yet. The relevancy of incretory hormonal imbalance during menstrual cycle to PMS or menstrual pains has been perceived.
There are several pathogeneses for PMS and menstrual pains. The pathogeneses may include considering those arising from the deficiency of progesterone, the excess secretion of estrogen and androgen, the excess secretion of pain-inducing prostaglandin, or the deficiency of vitamin B complex or essential fatty acids. In general, it is believed that PMS or menstrual pains occur due to the combination of the above-listed factors together with an environmental factor.
According to the most convincing pathogenesis for PMS and menstrual pains related with the excess secretion of prostaglandin, in the female menstrual cycle, as the secretion of a luteinizing hormone (LH), progesterone, stops, the pain inducing prostaglandin is secreted. As a result, tunica myometrium is contracted, and transient anemia and menstrual pains occur. According to this theory, to suppress such PMS or pains, the following methods have been suggested.
As a most widely used method, the production of prostaglandin is suppressed with the administration of, for example, aspirin or ibuprofen to relieve the menstrual pains. In another method, an anti-anxiety agent or anti-depressant, such as benzodiazepine, is used. Alternatively, progesterone is administered in the luteinizing phase of the female menstrual cycle.
In another treatment method, Korean Patent No. 0171408 discloses the use of melatonin (N-aceryl-5-methoxytryptamine), and Korean Laid-open Application No. 2001-0024462 discloses the use of serotonin (5-hydroxytryptamine).
Among a number of methods for treatment of PMS or menstrual pains, treatments with hormones, such as progesterone, melatonin, or serotonin, or with neurotransmitters in the luteinizing phase are known to be effective for relieving general pains, stress, chronic fatigue, and depression as well as PMS or menstrual pains.
However, those treatment methods of direct administration of hormones, such as melatonin or serotonin, cannot ensure 100% safety, and the cost of preparing the pharmaceuticals is high. Therefore, the treatment agents are not generally taken.
Yeast is known to respond sensitively to external conditions, compared to other microorganisms. Yeast has the ability to grow in both anaerobic and aerobic conditions, stops growing if the condition of a growth medium is unsuitable for growth, and undergoes heterozygosis to sustain itself under poor external environments. All organisms exhibit an alarm reaction when a stress is perceived for the first time and actively resists against the stress if the stress is not relieved to induce physiological changes for homeostasis (Seyle, 1956). The inventor has realized the present invention by combining the above characteristics of yeast and organisms. In particular, after full proliferation of yeast, the growth medium was subjected to physical and chemical stresses, such as high-temperature heating, ultrasonic waves or vibrations, and pH variations, of a degree not to causing destruction, to produce excess anti-stress substances such as proteins and enzymes. A yeast extract was prepared by autolysis or hydrolysis with a protease, and purified by ultrafiltration to attain yeast-derived peptides. Also, it was proven that the yeast extract and peptides have activities as brain-neurotrophins (derived from the natural source), therapeutic and prophylactic agents for the treatment of autonomic nerve disorders, such as an anti-stress agent, anti-anxiety agent, or sleeping aids, and PMS and menstrual pain relaxants, the PMS and menstrual pains showing similar symptoms to stress.